Protective circuits that prevent circuit elements from entering into a destructive mode of operation that might otherwise irreversibly cause deleterious effects to occur are known. These thermal shutdown circuits commonly use a NPN or PNP transistor as a thermal sensor which has a reference voltage placed across its base and emitter electrodes so as to establish a desired V.sub.be (emitter to base voltage) quantity. The circuit arrangement typically provides a reference voltage having a positive temperature coefficient so that it may offset or compensate for the V.sub.be characteristic of the thermal sensor which typically has a known negative temperature coefficient. The magnitude of the reference voltage is set so that it equals the V.sub.be quantity of the thermal sensor at a certain temperature. Below this temperature the thermal sensor is rendered off and above this temperature the thermal sensor is rendered on. Typically, this is a temperature that keeps the protective circuit out of the destructive mode and it is referred to herein as the thermal shutdown (TSD) temperature. In order for the TSD temperature to be accurately provided, the characteristic V.sub.be at that temperature must be predicted with certainty.
In conventional thermal shutdown circuits, the most significant variation in the TSD temperature is created by the uncertainty of the V.sub.be quantity of the thermal sensor due to fluctuations occurring in the process of fabricating the integrated circuit. These variations can be as large as 50 millivolts (mV) from its minimum to its maximum value and such a fluctuation translates to a range of about .+-.12.5.degree. C. variation in the TSD temperature. Furthermore, additional fluctuations are experienced due to small variations in circuit component mismatches, such as resistors and base current parameters.